1. Field of the Invention
The present invention relates to a lubricating structure of a planetary gear, and in particular, to a lubricating structure where the supply of lubricating oil to a gap between an inner peripheral surface of a pinion and an outer peripheral surface of a pinion shaft constituting the planetary gear is made efficient.
2. Description of the Prior Art
A conventional technique of this type is disclosed, for example, in Japanese Patent Laid Open Publication No. 61-48643. That is, the conventional technique disclosed in this Publication relates to a forced lubricating mechanism of a planetary gear of an automatic transmission for vehicles. In this lubricating mechanism, an oil reservoir is fixed to a side surface of a planet carrier to supply lubricating oil to an aperture in a pinion shaft end face. An oil path is formed in the inside of the pinion shaft. A bearing having a thrust race is disposed between the planet carrier and a ring gear supporting member adjacent thereto so that the thrust race of the bearing is made to abut against the ring gear supporting member. An outer peripheral portion of the thrust race is bent toward the planet carrier side to overlap with the aperture portion of the oil reservior, and furthermore, the planet carrier and the ring gear supporting member are made to receive a force at opposing sides thereof to each other. In this respect, as a concrete structure for making the the planet carrier and the ring gear supporting member to receive the force at opposing sides thereof to each other, in the case where a sun gear, a pinion, or a ring gear is transmitted with power in a direction of forward rotation while the vehicle is travelling, each gear is formed with a helical gear so that the sun gear and the ring gear supporting member receive a force at opposing sides thereof.
In such a structure, the lubricating oil flows outwardly in a radial direction between the planet carrier and the ring gear supporting member further, the lubricating oil flows through the bearing outwardly in the radial direction, and is supplied to the oil reservior so that the lubricating oil is supplied from the oil reservior to a bearing interposed between the outer peripheral surface of the pinion shaft and the inner peripheral surface of the pinion through the oil path in the inside of the pinion shaft, and to a thrust washer interposed between the planet carrier and the pinion end face. However, since the mutually opposing sides of the planet carrier and the ring gear supporting member receive the force, the thrust race of the bearing is pressed against the ring gear supporting member, and the formation of a gap between the thrust race and the ring gear supporting member is prevented. Thus, a large part of the lubricating oil flowing between the planet carrier and the ring gear supporting member is moved along the planet carrier so that a relatively large quantity of the lubricating oil can be supplied to the oil reservior reliably.
However, in the conventional technique disclosed in the publication, it is structured so that the planet carrier and the ring gear supporting member receive the force at mutually opposing sides thereof thereby to achieve advantageous effect as mentioned above. However, in order to realize this, it is necessary to form each gear with a helical gear twisted in a predetermined twisting direction, and depending on the twisting direction of the helical gear, it is impossible to divert a helical broach, which is used to manufacture other helical gears to manufacture the helical gear twisted in the predetermined twisting direction. A new helical broach, which meets the predetermined twisting direction, will be required resulting in the increase of manufacturing cost.
Furthermore, it is only during forward rotation that the thrust race is pressed against the ring gear supporting member. During reverse rotation, a gap is formed between the thrust race and the ring gear supporting member. The lubricating oil flows out through the gap. This creates a problem in that the amount of lubricating oil that can be supplied to the oil reservoir is decreased.
In this respect, in order to solve such a problem, it will be considered, for example, to provide a spring between the thrust race and the ring gear supporting member to press the thrust race against the ring gear supporting member. However, there is a drawback in that such a measure increases the number of parts, the man-hours, and the cost so that it is not an effective resolution.